Design And Implementation Of Very Low Frequency/Ultra Low Frequency Signal Analyzer Based On SOC

Very low frequency and ultra low frequency signals have been extensively studied in many scientific fields such as atmospheric science,geophysics science,geological analysis and vibration analysis.Traditional research equipment mainly includes common signal spectrum analyzers and specialized analysis equipment,which usually has incomplete frequency coverage and often lacks in size,power consumption and system performance.Some specialized equipments share similar structures but have limited analysis functions.Therefore,it is of great significance and value to research and design a highly integrated general purpose signal analyzer to provide spectrum analysis of ultra low and very low frequency signals.In the view of above issues,this thesis proposes a SOC-based VLF/ULF signal analysis architecture and detailed studies the hardware and software design of the signal analyzer.This thesis is mainly divided into the following sections :This thesis firstly analyzes the structure,advantages and disadvantages of traditional spectrum analyzers,and proposes system design indicators based on the characteristics of VLF/ULF bands and system design requirements.A complete design solution of signal analyzer is presented by decomposing design indicators.Both hardware and software design such as data acquisition solution,SOC-based digital signal processing scheme,system/user software design are discussed.Secondly,aiming at the problem of analysis performance degradation caused by spectral leakage in the traditional FFT spectrum analysis method,an all-phase data preprocessing method was used to pretreat the original sampling data,which can effectively reduce spectrum leakage and satisfied the needs of multi-tone signal and weak signal analysis in VLF/ULF bands.Thirdly,the hardware design of the data acquisition board and the SOC-based digital signal processing platform are presented according to the requirements.This thesis mainly covers the ADC peripheral circuit,power supply circuit,clock circuit,signal conditioning circuit designs on FMC data acquisition board and SOC startup circuit,FMC pin mapping and other circuit designs on carrier board.Moreover,this thesis utilizes SOC software and hardware co-odrination method and develops multiple custom IP cores such as ADC chip digital interface,decimation filtering module,all-phase FFT preprocess module,and data/command interaction module,which make full use of chip resources.The AXI bus technology is used to realize the data intercommunication between the programmable logic and the processing system.Based on the Linux operating system,the development of application software such as data exchange device driver,spectrum parameter estimation algorithm and Ethernet data transmission module is realized.The systematic tests of SOC-based signal analyzer shows that the hardware IP and system software are working properly.The system can analyze signal spectrum in VLF/ULF band correctly,which meets the demand of performing general spectrum analysis in these bands.